Segmented Dielectric Islands for Trench FET Contact Reliability
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Solution Overview
Problem
Conventional double layer metal (DLM) trench MOSFET structures are prone to cracks in the intermetal dielectric layer due to wire bond attachment, leading to unwanted shorts between source and gate contacts.
Innovation Solution
A reliable and robust electrical contact is achieved by patterning a contact pad from a first metal layer with multiple dielectric islands spaced apart by a second metal layer, preventing cracks from propagating and maintaining electrical isolation between source and gate contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contiguous intermetal dielectric is used between overlapping metal layers, then electrical isolation between source and gate contacts is achieved, but cracks can propagate through the dielectric layer causing shorts
Solution Approach 1:
The patent divides the contiguous intermetal dielectric layer into multiple separate dielectric islands, each surrounding individual metal layers. This segmentation prevents crack propagation across the entire dielectric structure, as cracks are confined to individual islands rather than propagating continuously between overlapping metal layers.
Solution Approach 2:
The patent applies different dielectric configurations to different regions: dielectric islands are formed around metal layers in regions susceptible to wire bond attachment stresses, while other regions maintain appropriate electrical isolation. This localized approach addresses stress concentration points without compromising overall electrical isolation.
2Reliability
If wire bond is attached to the source contact, then electrical connection is established, but stresses can cause cracks in the intermetal dielectric
Solution Approach 1:
The patent pre-configures the dielectric structure as separate islands before wire bond attachment, creating a stress-resistant architecture that cushions against the mechanical stresses of subsequent wire bond attachment. This preemptive structural design prevents crack initiation and propagation at the bond interface.
3Ease of manufacture
If a contiguous intermetal dielectric is used, then manufacturing is simplified, but crack propagation can occur
Solution Approach 1:
The patent implements dielectric islands through standard photolithography and deposition processes, where the dielectric material is deposited and then patterned to form separate islands. This segmentation can be achieved with minimal additional manufacturing steps while dramatically improving reliability by preventing crack propagation.
Data Source
AI summary
According to an embodiment of a method for fabricating a trench field-effect transistor (trench FET), the method includes: the method includes: patterning a contact pad from a first metal layer situated over a surface of an active die; forming a dielectric layer over the contact pad; patterning the dielectric layer to form a plurality of dielectric islands spaced apart from one another by respective voids; and forming a second metal layer between and over the plurality of dielectric islands so as to substantially fill the respective voids. The contact pad, plurality of dielectric islands, and second metal layer provide the reliable and robust electrical contact.